A number of devices and instruments such as calorimeters utilize liquid nitrogen or other liquified gas in a reservoir at very low temperature. Such instruments often have a cooled ("cryogenic") working surface that normally is enclosed under a cover during operation of the instrument. When the cover is opened for insertion, removal or manipulation of samples for test, the working surface and samples are exposed to ambient air. Humidity in the air generally condenses or frosts the working surface and samples unless protection is provided. Conventional protection is provided by a dry box which is placed as a cover over the working area at least during the time of sample manipulation. Such a box has dry air or nitrogen passed in at a slight pressure, holes with a pair of gloves extending into the box, and an interlock for passing through samples. This system is quite cumbersome to use, particularly in the manipulation of delicate samples with tweezers while using the gloves.
Laminar gas flows have been used for doorways to minimize the mixing of outside with inside air, so that people can pass through without opening doors, for example to protect the inside against temperature extremes or medical contamination. Laminar flow hoods have been used for working with materials subject to, or causing external contamination, such as in forensics. Another application for laminar flow has been the cooling of gas turbine blades.